GypsyComet
SOC-14 1K
There is no reason to believe there was a massive die back on former Imperial worlds just because there is no interstellar trade. Pocket empires would have sprung up, worlds could still maintain some contact via STL methods - the way the Vilani spread into space in the first place.
Politics became local, to paraphrase a common thought.
Because the first two centuries or so after the declared beginning were a period of slow but recognized withdrawal, pocket empires would certainly have remained behind. Small cultural zones around strong worlds who dared to defy the coming darkness.
I think there was retreat and retrenching, as many of the little specialized colonies and outposts saw the writing on the wall and picked up stakes for the nearest High Population center. The Solomani had inundated the former First Imperium with settlers who were not at all picky, so there were a lot of systems with young settlements two centuries later. How those would have been treated by the majority Vilani old Hi Pops as the retreat began would have run the gamut, and been a precursor to the real darkness.